JPS61217159A - Artificial acetabulum equipped with holder and acetabulum insert - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an artificial acetabulum comprising a metal retaining member and a plastic acetabular insert, the retaining member comprising:
a ring-shaped closed stock for the acetabular insert on the medial surface, an e-surface and a central positioning surface forming a cylindrical medial surface adjacent to the receiving opening; in which the stop surface is spherically or conically shaped or otherwise tapered, and the central positioning surface has an annular undercut or groove that connects at least indirectly to the stop surface; Regarding.

An acetabular prosthesis of this type as disclosed in EP 65 482 has an annular expansion ring which is connected to the retaining member and the inner plastic acetabular insert. The retaining member and the acetabular insert are evenly engaged in adjacent corresponding notches to prevent relative axial displacement of the retaining member and the acetabular insert. This expansion ring must be guided axially precisely enough to enable the desired snapping effect. The disadvantage in this case is that the expansion ring serves to transmit the forces that occur during loading of the acetabulum from the acetabular insert to the holding element. In this known artificial acetabulum, the acetabular insert further has a collar projecting downward, and this collar is in contact with the edge of the ring-shaped retaining member, so that the retaining member can be moved from the acetabular insert to the retaining member. The characteristics of force transmission to are not specified in any case. Furthermore, this known acetabular prosthesis has the disadvantage that there is a risk of losing the expansion ring.

In the acetabular insert disclosed in EP 66092, the acetabular insert can be snapped onto a retaining member forming the lateral acetabulum using an annular projection. However, in this known arrangement, the outer shell and the inner shell are preferably made of tissue-compatible plastic, and a buffer layer is inserted between the two shells. If the elastic damping properties of the damping layer are desired to be effective in this case, there is a radial play between the inner and outer shells which defines a fairly large radial interference of the locking means. It must exist. Since the entire inner shell can be deflected laterally, there is no risk that the locking means will fly out of the recess receiving them and that a stable locking of the acetabular insert is no longer guaranteed. be. In the unlocked state, the acetabular insert may be brought into an unstable position during subsequent load cycles. Furthermore, when plastic members are combined, deformation on both sides under load must be taken into account, so the radial tightening margin must be large.

Therefore, the object of the invention is to provide a holding element which already has a conical or other shaped tapered stone ξ surface for force introduction in the upper inner region from the acetabular insert. The force transmission to the retaining element takes place in precisely defined ranges so that the snap connection between the acetabular insert and the retaining element is maintained as easily as possible without the need for additional elements. , and to ensure that it is released with as little load or movement as possible.

Means for Solving the Problem In order to solve this problem, the present invention provides an artificial acetabulum of the type mentioned above, in which the acetabular insert is undercut for snap connection with the retaining member. It has mating annular projections and/or a cylindrical outer surface in the edge region, which outer surface is aligned with the inner central positioning surface and is provided with an interference fit as a clamping seat. .

OPERATIONS AND EFFECTS OF THE INVENTION By the means according to the invention, the inner shell or acetabular insert is centered and occupies a defined position within the outer shell or retaining member. The introduction of the maximum pressure load takes place at the same time in the area of the centrally located conical contact surface. Additional central positioning takes place in the area of the cylindrical surface in the edge area near the opening for inserting the acetabular insert. This prevents the acetabular insert from shifting in the radial direction, on the one hand, and eliminates the risk of tilting, on the other hand, so that a relatively narrow collar or slight interference is required to hold the acetabular insert. It is sufficient to provide it in the edge area.

Nevertheless, the acetabular insert itself accepts elastic deformations, so that impact loads can be well absorbed.

The fact that the acetabular insert is made of plastic provides a sufficient damping effect, especially because polyethylene is preferably used as the material. The metal outer ring or retaining element also ensures that the engagement properties are stable, especially in the acetabulum, and that the contact surface for the acetabular insert under load also remains sufficiently geometrically precise.

Precise centering of the acetabular insert results in minimal protrusion of the locking means, allowing removal and snap-on of the acetabular insert for replacement while the outer retaining member remains implanted. can. Thus, the combination of a resilient plastic acetabular insert with a metal retaining element that can self-cut into the acetabulum and remain securely there is of great advantage. This is advantageous, in particular, for the following reasons: the retention element fixates over time and its position becomes increasingly stable, so that its removal does not place unnecessary loads on the patient or risk damage to the bone. . The problem-free exchange of the acetabular insert makes reoperations relatively easy; the acetabular insert can be exchanged without difficulty, in which case the retaining element is not deformed and thus the position of the retaining element in the bone is changed. Instead, the deformation required for locking is taken up mostly by the acetabular insert.

The contact surface for transmitting the force from the acetabular insert to the holding element is located in the anterior tapered region, and the axial centering of the acetabular insert takes place in this region as well as in the vicinity of the edge region of the opening. Therefore, the acetabular insertion training part located between both regions and having the snap connection means can be sufficiently elastic to carry out the movements necessary for the snap connection.

In a further embodiment of the invention, a slight interference of the acetabular insert in the region of the cylindrical surface near the edge region serves for the necessary locking. Of course, even if a snag occurs due to the cylindrical tightening, the defined orientation of the acetabular insert obtained by the measures according to the invention is such that the holding force makes it possible to exchange the acetabular insert. is necessary.

The invention is further based on the recognition that the retaining ribs of the self-cutting acetabular prosthesis are stably fixed inside the acetabulum, and that the retaining ribs are similar to the surface of the plastic acetabular insert. , serves to introduce forces that load the hip joint into the acetabulum. Furthermore, the tapered inner surface of the retaining member provides a stop surface for receiving and transmitting forces in the vicinity of the retaining surface to a radial portion of the retaining member. As already mentioned, the surgeon can choose between two alternative configurations: an acetabular insert made of high-molecular-weight polyethylene is pushed together with a ring-shaped insert into the retaining member with a small force. and is movable in the axial direction within the holding member, with inadvertent dropout being prevented by the tightening of the cylindrical center positioning surface. Additionally, if the clinician desires a releasable connection, the retention member may be provided with an undercut in the central locating surface and a corresponding edge beveled at an angle in the direction of introduction of the acetabular insert so that the two snap together. With this configuration, the acetabular insert can be removed from the retaining member without damage. In this case the acetabular insert does not need to have any interference.

In an advantageous embodiment of the invention with a snap-fittable annular edge as a locking device, the annular projection of the acetabular insert, which engages in the recess of the holding element, has a tongue-shaped cross section. and is adjacent to the lateral surface of the acetabular insert via an annular groove on each side of the tongue. With this configuration, the area projecting from the outer contour of the acetabular insert is extremely flexible, and the acetabular insert can be inserted with little force. Furthermore, the recess in the holding element in which the locking web with the tongue-like cross section engages can likewise be designed as a groove, in which case the holding element can be secured by means of a snap-fitting tongue ring. It is the same as a general purpose retaining member connected to the acetabular insert. Therefore, with this configuration, inventory management becomes extremely easy.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The holding element 1 shown in FIG. Thread segments 2 are provided, which are separated from one another by separating grooves 3.

The thread segment 2 has a sharp edge in the part that precedes it when screwed in and projects most from the spherical surface in this part. The thread segment 2 forms a sharp-edged tip in the region of the separating groove 3 . In the region located further back in the direction of rotation during screwing, the thread segment 2 has an obtuse to flattened configuration towards its outer edge, which can be positioned one above the other by milling or similar means. This can be done by machining the thread segments parallel to each other. The ring-shaped retaining element 1 is preferably made of a titanium alloy, the elastic properties of which with suitable cross-sectional dimensions approximately correspond to the elastic properties of the surrounding bone.

The acetabular insert 5 is adapted to the internal cross-sectional dimensions of the holding element 1 and can be inserted from below into the holding element 1 already screwed into the bone. In this case, the hemispherical upper region 6 of the acetabular insert 50 protrudes from the holding element 1 and, in the inserted state, is supported inside a recess provided in the bone.

FIG. 2 shows the retaining element 1 and the acetabular insert 5 in principle in cross-section. The two parts 1.5 each have conically shaped regions (surfaces 8; 9) which are joined to one another. The applied force is introduced via the side surface (9) of the frustoconically tapered region into the holding element region (8) which forms a correspondingly configured recess. The acetabular insert 5 shown in FIG. 2 has on its underside a recess 10 for receiving the head of a femoral prosthesis. The cylindrical inner surface 11 of the holding element 1 and the outer surface 12 of the acetabular insert 5 likewise serve for axial centering. The surfaces 8, 9 thus cooperate with the cylindrical surfaces 11, 12 of slight height to center the retaining element 1 and the acetabular holder 1 by centering and limiting the travel of the acetabular insert 5. A relatively defined guidance with the insert 5 is implemented. The drawings described below correspond to the area (■) indicated by the dashed line in FIG.

It is an enlarged view of ■.

3a to 3c are partial cross-sectional views of a rotationally symmetrical prosthetic acetabulum, the cross-section being located in a radial plane. These figures only show the area of the contact surface between the retaining element and the acetabular insert. FIG. 3a shows in cross-section the area of the inner surface of the retaining element 1, where the surface 8 forms the tapering stop surface of the acetabular reservoir, the stop surface 779 of which is implanted. It works to transmit the force acting on the acetabulum in the held state to the holding member 1.

A step 13 follows the surface 8 and forms an undercut for the cylindrically designed surface 11.

Between the step 13 and the stop surface 8 there is likewise an approximately cylindrical surface 14 which is connected to a retaining element (an annular projection 15 in FIG. 3b) which engages the end of the undercut. ) allows for axial movement.

FIG. 3b shows the outer contour of the first acetabular insert 5 in cross-section, the outer surface 9 of which is aligned with the inner surface 8 of the holding element 1. FIG. Whereas the cylindrical surface 12 of the acetabular insert 50 has some play with respect to the surface 11 of the retaining member 1, the projection 150 dimensions are the same when the acetabulum is unloaded. The lower edge of the protruding portion 15 is set to come into contact with the corresponding surface (step portion 13) of the holding member 1. The acetabular insert 5 is also slightly shiftable, so that under load the surface 9 of the plastic acetabular insert 5 can come into contact with the surface δ of the retaining member 10 and the acetabular insert 5 The protrusion 15 prevents it from falling off. Annular protrusion 1 when shifting axially under load
5 moves over surface 14.

The acetabular part shown in FIG.
It can be snapped onto the retaining member shown in Figure a with a small pressing force.

That is, in the embodiment shown in FIGS. 3a and 3b, the pressing forces that occur during loading are also centered on the acetabulum in the surfaces 8, 9; 11.12, in which case the central positioning takes place mainly via the surfaces 8, 9; of the acetabulum, with
The area located close to the opening is guided within extremely narrow tolerances, so that the width of the stone rim (15) can be relatively small, so that the width required for the insertion of the acetabular insert is relatively small. Deformations can be effected by hand. Additionally, tilting is also avoided. It is therefore easily possible to remove the acetabular insert 5 again by introducing manual force. A suitable protrusion value for the protrusion 15 is about 0.4 km.

It should also be taken into account that due to the elastic configuration of the acetabular insert, the acetabular insert can be adapted by deformation to the given nature of the endograft, in which case the cylindrical The shaped faces 11.12 are such that the protruding edges engage.

In the acetabular insert 5' shown in FIG. 3C, the retaining member 10
a cylindrical surface 12' forming a collar, mated to surface 11;
has a slight tightening margin, so the acetabular insert 5
' contacts the retaining member 1 under load with its outer surface and is also shiftable in response to the load action but does not fall off due to the tightening of the diameter of the cylindrical surface. However, the acetabular insert 5' can be withdrawn from the holding element 1 at any time if required.

In the embodiment shown in FIG. 3C, the primary load is also on surface 9'.
to the corresponding surface 8 of the holding member 1. The cylindrical surface 12' has an interference, in which case the acetabular insert 5' is held firmly in response to the indentation on this surface 12' under the forces expected in use and also in the acetabular It is designed so that it cannot come off even under a load that tilts the mortar insert 5'.

The embodiment shown in FIG. 4a shows a known construction of a retaining element 1' with an annular groove 16 of square cross section. The acetabular insert 5'' according to the invention (FIG. 4b) used in this holding element 1' has a tongue-shaped projection 17 on both sides, which has grooves 18, 19,
limited by. The tongue-shaped projection 17 projects only slightly beyond the outer contour of the remaining acetabular insert ridge, so that the acetabular insert 5' can be moved with a small force into the retaining member 1 shown in FIG. 4a. ’ can be inserted. However, it is also possible to use the acetabular insert 5'' with the retaining member 1 shown in FIG. 3a. Accordingly, a number of insertions and removals of the acetabular insert are possible.The projection 17 with a tongue-shaped cross section is preferably beveled on the outside, so that the acetabular insert can be inserted and removed several times. The tapering in the direction of introduction facilitates a snap connection during insertion, but avoids inadvertent dislodgement.

The advantageous dimension of the width of the tongue in cross section is approximately 0°7ffI
I11, each groove lδ having a semicircular cross section
, 19 is 0.5 rm. In this case, the tongue-like projection 17 protrudes by approximately 0.4 a+ compared to the remaining external contour of the acetabular insert 5'' and may, if necessary, prevent a snap connection during insertion of the acetabular insert. Advantageously, it can be rounded or beveled with a relatively large radius in cross section.

The tongue-like projection 1 17 has a relatively large lateral movement, so that it can move into the contour of the acetabular insert 5'' when subjected to radial loads. It crawls in and advances again as soon as groove 16 is reached.

The acetabular insert is also radially centered by a tapered front surface that is aligned with the corresponding inner surface of the retaining member so that the acetabular insert is oriented concentrically with respect to the retaining member. ing. With this configuration, the acetabular insert does not move in the radial direction even under load, so that the snap-fitting projection and the groove receiving the crest projection or a suitable attachment device can be The acetabular insert will not become dislodged and the acetabular insert will not become undesired. Nevertheless, the acetabular insert made of polyethylene is elastically deformable, especially in its open region, so that the acetabular insert can also absorb forces that occur in an impact manner. In addition to this, it is also advantageous that universal components can be used.

In the embodiment shown in FIG. 4b, the cylindrical surface 12 serves for axial orientation, so that the projection with tongue-shaped cross section only needs to project slightly. 3rd b
Edge 2 corresponding to the edge of the protrusion 15 in the illustrated embodiment
0 prevents the acetabular insert from falling out of the retaining member 1', whereas the opposite edge 21 may have some play. In the configuration shown in FIG. 4b, the tongue-like protrusion 17, by virtue of its elasticity (and suitable deflection) during manual insertion or removal of the acetabular insert, forms a groove 18; 19 which forms a notch. It is extremely easy to handle. The tongue-shaped protrusion 17 is
It forms a relatively elastic locking device that can be moved slightly towards both sides, so that it can follow deformations of the holding element or the acetabular insert, in this case the introduction of the main force. is similarly performed in the area of surfaces 8 and 9.

The double centering prevents lateral movement and tilting of the acetabular insert, so that the protrusion 17 with tongue-like cross-section can be positioned in the acetabular position even if the retention depth is relatively shallow. Hold the insert firmly.

No special tools are required for insertion and removal of the acetabular insert, and the appropriate steps can be performed directly by hand.

By selecting a suitable acetabular insert, the physician can take into account the individual holding capacity of the patient's acetabulum, along with a wide variety of other conditions.

The configuration of the invention is not limited to the advantageous embodiments described above, but a large number of variant embodiments are possible using the solution described above in completely different types of configurations.

[Brief explanation of drawings]

FIG. 1 is a side view of the retaining member with a plastic acetabular insert inserted, FIG. 2 is a sectional view of the retaining member shown in FIG. 1, and FIG. 3a shows one embodiment of the retaining member. Figures 3b and 3c are partial sectional views showing two embodiments of the acetabular insert; Figure 4a is a partial sectional view showing another embodiment of the retaining member; FIG. 7 is a partial cross-sectional view of yet another embodiment of an acetabular insert. 1.1'... Holding member, 2... Thread segment,
3... Separating groove, I... Tip, 5.5', 5"...
Acetabular insert, 6...upper range, 8.8', 9.9'
, 9'', 11, ll', 12, 12', 12
f, 14... Surface, 10... Notch, 13... Step part, 15.17... Projection part, 16.18, 19...
Groove, 20.21...edge! 71'・-4L@member sr, y"-... is the bone mound λ I5.77- Ashisha part

Claims (1)

[Claims] 1. An artificial acetabulum comprising a metal holding member and a plastic acetabular insert, wherein the holding member has an inner surface for the acetabular insert. It has a ring-shaped closed stop surface and a central positioning surface forming a cylindrical inner surface adjacent to the receiving opening, in which case the stop surface has a spherical or conical shape or a different shape. of the type in which the acetabular insert (5) is tapered and the central positioning surface has an annular undercut or groove connecting at least indirectly to the stop surface, the acetabular insert (5) an annular projection (15, 17) adapted to the undercut for a snap connection with (1) and/or a cylindrical outer surface (12) in the edge region; Artificial acetabulum with a retaining element and an acetabular insert, characterized in that the outer surface (12) is aligned with the inner centering surface (11) and is provided with an interference fit as a clamping seat. 2. The tightening margin or surface (12) of the protrusions (15, 17)
') and the elastic properties of the plastic of the acetabular insert (5) such that insertion of the acetabular insert (5) can be carried out by manual pressure without the aid of a tool. 2. Acetabulum prosthesis according to claim 1, which are mated together. 3. The projections (15, 17) have an oblique chamfer that tapers in the direction of insertion of the acetabular insert (5);
An artificial acetabulum according to claim 1 or 2. 4. The annular projection (17) has a tongue-like cross section, only the area of the tongue protrudes from the outer contour of the acetabular insert, and the tongue has a width of 0.7 mm. , claim 1
The artificial acetabulum according to any one of paragraphs 3 to 3. 5. A groove (1) adjacent to at least one side of the protrusion (17)
8, 19) is provided, the artificial acetabulum according to any one of claims 1 to 4. 6. Artificial acetabulum according to claim 5, wherein the grooves (18, 19) have a radius of approximately 0.5 mm. 7. Claim 1, wherein the stop for the acetabular insert (5) in the direction of insertion into the holding element (1) is formed primarily by a stop surface (8).
The artificial acetabulum according to any one of paragraphs 6 to 6. 8. The protrusion value of the protrusion (17) is approximately 0.4 mm;
An artificial acetabulum according to any one of claims 1 to 7. 9. The artificial acetabulum according to any one of claims 1 to 8, wherein the holding member (1) is made of a titanium alloy that is compatible with the human body. 10. Artificial acetabulum according to any one of claims 1 to 9, wherein the acetabular insert (5) consists of high molecular weight polyethylene.